A161691 Number of reduced words of length n in the Weyl group A_46.

1, 46, 1080, 17249, 210748, 2100337, 17779207, 131436629, 865982661, 5164024608, 28210551124, 142564402050, 671834963239, 2972133119783, 12413240052842, 49183360339945, 185647433835908, 670019931232182, 2319603230895916

Offset

0,2

Comments

Computed with MAGMA using commands similar to those used to compute A161409.

References

J. E. Humphreys, Reflection Groups and Coxeter Groups, Cambridge, 1990. See under Poincaré polynomial.

N. Bourbaki, Groupes et alg. de Lie, Chap. 4, 5, 6. (The group is defined in Planche I.)

Links

Table of n, a(n) for n=0..18.

Formula

G.f. for A_m is the polynomial Prod_{k=1..m}(1-x^(k+1))/(1-x). Only finitely many terms are nonzero. This is a row of the triangle in A008302.

Crossrefs

Sequence in context: A057465 A035718 A246993 * A162186 A162452 A010998

Adjacent sequences: A161688 A161689 A161690 * A161692 A161693 A161694

Keyword

nonn

Author

John Cannon and N. J. A. Sloane, Nov 30 2009

Status

approved